Shelley spent 17 minutes washing the dishes. she spent 38 minute cleaning her room. Explain how can use mental math to find how long shelley spent on the two tasks.

If we would using mental math, we would estimate the washing dishes to 20 minutes, and cleaning 40 min,

together 20+40 min

is 60 minutes, aprox 1 hour

Shelly spent almost 1 hour cleaning